Plunger suitable for use in a glassware forming machine

Abstract

The plunger comprises a base portion adapted to be mounted on a piston rod and a tip portion which has a glass-engaging surface and a projection which enters a recess in the base portion. A generally cylindrical passage is defined by the base portion and the projection of the tip portion, the portion of the wall of the passage defined by the base portion being screw-threaded. A screw-threaded member is threadedly received in the passage and serves to retain the tip portion on the base portion by engaging a lip of the projection which projects across a portion of the passage.

We claim: 
     
       1. A plunger suitable for use in a glassware forming machine in forming parisons of molten glass for subsequent formation into an article of glassware, the plunger comprising a base portion adapted to be mounted on a piston rod of a piston and cylinder assembly to be moved by operation of the assembly into or out of a mould cavity in which the parison is formed, the base portion defining a recess which, when the base portion is mounted on a piston rod as aforesaid, opens towards the mould cavity, the plunger also comprising a tip portion having a surface arranged to engage molten glass in the mould cavity, and a projection which is adapted to be received in the recess of the base portion, wherein the base portion and the projection of the tip portion co-operate, when the projection of the tip portion is received in the recess of the base portion, in defining a generally cylindrical passage extending, from an opening at a point where the tip portion emerges from the recess into the base portion and the projection of the tip portion, the portion of the wall of the passage which is defined by the base portion being formed with screw threads and and the portion of the wall of the passage which is defined by the projection terminating in a lip of the projection which extends substantially transversely across a portion of the passage, and the plunger also comprising an externally-screw threaded member adapted to be inserted into the passage so that the thread of the member engages the threads of the wall of the passage so that the member is retained in the passage and the member engages the lip so that the member acts to retain the projection in the recess and hence the tip portion on the base portion. 
     
     
       2. A plunger according to claim 1, wherein the base portion defines a chamber communicating with said recess, said chamber providing communication between air passages formed in the base portion and air passages formed in the tip portion. 
     
     
       3. A plunger according to claim 1, wherein the passages extends at an angle of between 20° and 30° to a central longitudinal axis of the plunger.